From mboxrd@z Thu Jan  1 00:00:00 1970
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
Subject: Re: [PATCH] imx-drm: imx-hdmi: fix hdmi hotplug detection initial
 state
Date: Mon, 9 Jun 2014 20:29:03 +0100
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To: Fabio Estevam <festevam@gmail.com>
Cc: devel@driverdev.osuosl.org, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Tim Harvey <tharvey@gateworks.com>, DRI mailing list <dri-devel@lists.freedesktop.org>, Philipp Zabel <philipp.zabel@gmail.com>, Shawn Guo <shawn.guo@freescale.com>
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On Mon, Jun 09, 2014 at 03:15:16PM -0300, Fabio Estevam wrote:
> With HDMI cable connected (no image is seen on HDMI, only on lvds cable):
> 
> imx-drm display-subsystem.11: bound 120000.hdmi (ops hdmi_ops)
> imx-hdmi 120000.hdmi: EVENT=plugin
> imx-hdmi 120000.hdmi: Non-CEA mode used in HDMI
> imx-hdmi 120000.hdmi: final pixclk = 0

Right, so it does know that the HDMI sink is connected...

> imx-drm display-subsystem.11: bound ldb.10 (ops imx_ldb_ops)
> imx-hdmi 120000.hdmi: imx_hdmi_setup DVI mode
> imx-hdmi 120000.hdmi: got edid: width[51] x height[28]
> imx-hdmi 120000.hdmi: Non-CEA mode used in HDMI
> imx-hdmi 120000.hdmi: final pixclk = 138500000
> imx-hdmi 120000.hdmi: imx_hdmi_setup DVI mode
> imx-hdmi 120000.hdmi: Non-CEA mode used in HDMI
> imx-hdmi 120000.hdmi: final pixclk = 138500000
> imx-hdmi 120000.hdmi: imx_hdmi_setup DVI mode

And the mode it's setting has a pixel clock frequency of 138.5MHz here.

> If I disconnect/reconnect the HDMI cable (then image is seen on both
> HDMI and LVDS):
> 
> root@freescale /$ imx-hdmi 120000.hdmi: EVENT=plugout
> imx-hdmi 120000.hdmi: EVENT=plugin
> imx-hdmi 120000.hdmi: Non-CEA mode used in HDMI
> imx-hdmi 120000.hdmi: final pixclk = 138500000
> imx-hdmi 120000.hdmi: imx_hdmi_setup DVI mode
> imx-hdmi 120000.hdmi: got edid: width[51] x height[28]
> imx-hdmi 120000.hdmi: Non-CEA mode used in HDMI
> imx-hdmi 120000.hdmi: final pixclk = 138500000
> imx-hdmi 120000.hdmi: imx_hdmi_setup DVI mode
> imx-hdmi 120000.hdmi: Non-CEA mode used in HDMI
> imx-hdmi 120000.hdmi: final pixclk = 138500000
> imx-hdmi 120000.hdmi: imx_hdmi_setup DVI mode

And here it again configures 138.5MHz pixel clock - same as above.  So,
from this we can't see any difference in the setup, and we can say that
it's not mode->clock which is the problem.

> Now booting the kernel with HDMI disconnected:
> 
> imx-hdmi 120000.hdmi: Detected HDMI controller 0x13:0xa:0xa0:0xc1
> imx-hdmi 120000.hdmi: hdmi_set_clk_regenerator: samplerate=48000
> ratio=100  pixelclk=74250000  N=6144 cts=74250
> imx-drm display-subsystem.11: bound 120000.hdmi (ops hdmi_ops)

Right, so here it knows that there's nothing connected.

> imx-drm display-subsystem.11: bound ldb.10 (ops imx_ldb_ops)
> Console: switching to colour frame buffer device 128x48

So it selects an initial mode based upon the LVDS device configuration.

> And after connecting the HDMI cable:
> 
> imx-hdmi 120000.hdmi: EVENT=plugin
> imx-hdmi 120000.hdmi: Non-CEA mode used in HDMI
> imx-hdmi 120000.hdmi: final pixclk = 0
> imx-hdmi 120000.hdmi: imx_hdmi_setup DVI mode
> imx-hdmi 120000.hdmi: got edid: width[51] x height[28]
> imx-hdmi 120000.hdmi: Non-CEA mode used in HDMI
> imx-hdmi 120000.hdmi: final pixclk = 78800000
> imx-hdmi 120000.hdmi: imx_hdmi_setup DVI mode
> imx-hdmi 120000.hdmi: Non-CEA mode used in HDMI
> imx-hdmi 120000.hdmi: final pixclk = 78800000
> imx-hdmi 120000.hdmi: imx_hdmi_setup DVI mode
> 
> Image is seen on both LVDS and HDMI monitor, but HDMI resolution is
> not correct (this is a different bug though).

I'm guessing that here, DRM kept the original configuration rather than
selecting one appropriate to the newly connected device.

-- 
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